DESCRIPTION It is known that transcription factors mediate the distinct lineage differentiation of multi-potential hematopoietic stem cells. For instance, Pu.1 expression is essential for the development of monocytic cells while C/EBPalpha is essential for the development of granulocytic cells. However, the molecular basis for how one transcription factor is able to transactivate target gene expression in a multi-potential cell, while another factor is not, remains an enigma. The purpose of this proposal is to determine if the p300 co-activator protein and the SMRT co-repressor protein act as controlling factors to influence transcription factor mediated signals in hematopoietic stem cell that ultimately results in the determination of a specific lineage.